1. Field of the Invention
The present invention relates to a device which performs the drive control of two hydraulic actuators. In addition, the present invention relates to a device which performs the drive control of a boom hydraulic actuator and a bucket hydraulic actuator such that a posture of the bucket provided in the hydraulic drive machine is held constant.
2. Description of the Related Art
Booms and buckets are provided as work devices in construction machine such as wheel loaders and skid-stair loaders and so on.
By way of example, using a wheel loader, work is performed in which, following the excavation of the earth and sand with the bucket, the boom is raised whereby the earth and sand within the bucket is loaded into a dump truck. For the boom to be actuated in the upward direction during this work operation, the bucket must be actuated in the dumping direction in such a way that the posture of the bucket is held in a constant horizontal state with respect to the ground surface. This horizontal hold control is indispensable in preventing the earth and sand and so on within the bucket from spilling.
However, when the above-noted horizontal hold control is entrusted to the manual operation of the operator only, the dual operation of a boom operation unit and bucket operation unit must be performed. This dual operation places a large burden on the operator and requires experience. For this reason, an invention in which the abovementioned horizontal hold control can be performed without burden on the operator, and for which no experience is required, has been hitherto well known. That is to say, an invention in which the boom and the bucket are simultaneously actuated by the boom operation unit to perform horizontal hold control has been hitherto well known.
By way of example, an invention in which the boom and arm of a wheel loader are linked by a linking mechanism and, the posture of the bucket is held horizontal by the actuation of the bucket at a constant relationship established by the link mechanism in response to the actuation of the boom has been hitherto well known.
However, according to this invention, a special link mechanism must be manufactured in accordance with the type of work device. In addition, the link mechanism cannot be installed easily in existing construction machine and new work devices must be manufactured. For this reason, there are problems in that this lacks versatility.
In addition, Japanese Patent Application Laid-Open No. 10-219730 describes an invention in which return pressured oil discharged from a boom hydraulic cylinder is, in such a way that the posture of the bucket is held horizontal, branched by a branching valve to be supplied to a bucket hydraulic cylinder.
However, the abovementioned branching valve must be provided between an operation valve and the hydraulic cylinder. For this reason, the laying of the pressured oil conduits is complicated. In addition, a problem arises in that the hydraulic apparatus, through which a large flow rate of pressured oil of high pressure passes, is of large scale. In addition, because the flow rate which drives the actuator is branched, changes in the flow rate are dependent on the load. For this reason the operator must, to maintain the horizontal posture, be constantly carrying out minute operations. In other words, there are the problems that, because control is difficult, the burden on the operator is large and experience is required.
Thereupon, the present invention, which has excellent versatility, in which the pipe laying can be configured easily, in which the hydraulic apparatus can be compacted by the manipulation of pilot pressured oil, and in which no burden is placed on the operator, was designed to resolve these problems.
A first invention of the present inventions provides, in order to achieve the above-noted resolution of the problems, a hydraulic drive machine which comprises: a hydraulic pump (1), and at least two hydraulic actuators (2, 3) driven by supply of discharged pressured oil from the hydraulic pump (1); operation means (4, 5) provided correspondent with the hydraulic actuators (2, 3); and operation valves (6, 7) connected between each of the operation means and each of its correspondent hydraulic actuator which respectively change opening amounts thereof in accordance with operating amounts of the operation means (4, 5), and which supply pressured oil to the hydraulic actuators (2, 3) correspondent with the operation means (4, 5), at a flow rate according to the respective opening amounts, wherein
the machine comprises front-to-rear differential pressure constant means (8, 9) connected between the hydraulic pump and each of the operational valves which equalize a difference in pressure between a pressure of pressured oil on an upstream side and a pressure of pressured oil on a downstream side of the operation valves (6, 7) respectively, and wherein
when one of the operation means (4) of the operation means (4, 5) is operated, by changing the opening amount of the other operation valve (7) correspondent with the other operation means (5) in accordance with the operation amount of the operation means (4), the other hydraulic actuator (3) correspondent with the other operation valve (7) is driven.
A description of the first invention is given below with reference to FIG. 1 and FIG. 3.
Based on the general formula for a hydraulic circuit, the following formula (1) is established, when Q is the flow rate which passes through the diaphragm of the operation valve, c is the flow rate coefficient, A is the opening surface area of the diaphragm, and xcex94P is the front-to-rear differential pressure of the diaphragm
Q=cxc2x7Axc2x7{square root over ( )}xcex94P)xe2x80x83xe2x80x83(1)
Here, by constantly making the differential pressure xcex94P identical, a flow rate is obtained which is proportional to a drive command value (opening surface area A) issued by the operator.
According to the first invention, the differential pressure xcex94P between the pressure of the pressured oil on the upstream side and the pressure of the pressured oil on the downstream side of the operation valves 6, 7 is equalized by the front-to-rear differential pressure constant means 8, 9. As a result, from the above-noted formula (1), the flow rates Q1, Q2 of the operation valves 6, 7 are, irrespective of load fluctuations, determined univocally in accordance with the opening surface areas (opening amounts) A1, A2 of the operation valves 6, 7.
When one of the operation means 4, 5, the operation means 4 for example is operated, the opening amount A2 of the other operation valve 7 correspondent with the other operation means 5 is altered in accordance with the operation amount S1 of said operation means 4, and the other hydraulic cylinder 3 correspondent with said other operation valve 7 is driven.
That is to say, the ratio of the opening amount A1 of the operation valve 6 and the opening amount A2 of the operation valve 7 with respect to the operation amount S1 of the one operation means 4 is, as shown in FIG. 3(b), set to a constant relationship (b:a). For this reason, the ratio of the flow rate Q1 supplied to the hydraulic cylinder 2 correspondent with the operation valve 6, and the flow rate Q2 supplied to the hydraulic cylinder 3 correspondent with the operation valve 7, form the above-noted constant relationship (b:a).
According to the first invention as described above, by way of example, a boom hydraulic cylinder 2 and bucket hydraulic cylinder 3 can be simultaneously driven at a constant flow rate ratio by the operation of the boom operation unit 4 only.
In this case, since the ratio of the opening amount A1 of the operation valve 6 and the opening amount A2 of the operation valve 7 with respect to the operation amount S1 of the operation means 4 only needs to be set to a constant relationship, the device configuration, such as the laying of the pressured oil conduits, is simple. That is to say, for example, a shuttle valve 50 and a pilot conduit 18b only should be newly provided such that a pilot pressure P in accordance with the operation amount S1 can be supplied to the operation valves 6, 7. In addition, the operation valves 6, 7 (the spool) should be configured in such a way that the ratio of the opening amounts A1, A2 of the operation valves 6, 7 form a constant relationship.
In addition, according to the first invention, the shuttle valve 50 and the pilot conduit 18b only are newly provided, and the operation valves 6, 7 (the spool thereof) only needs to be configured such that the ratio of the opening amount A2 of the operation valve 7 and the opening amount A1 of the operation valve 6 with respect to the operation amount S1 of the boom operation unit 4 is set to a constant relationship. For this reason, it can be easily installed in existing hydraulic circuits.
In addition, according to the first invention, the pilot pressured oil of low pressure and small flow rate is used, so the hydraulic apparatus can be compacted.
As a result, according to the first invention, high versatility can be obtained, the pipe laying can be configured easily and, by virtue of the fact that the pilot pressured oil is managed, the hydraulic apparatus can be compacted.
In addition a second invention provides a hydraulic drive machine which comprises: a hydraulic pump (1), and a boom hydraulic actuator (2) and a bucket hydraulic actuator (3) driven by supply of discharged pressured oil from the hydraulic pump (1); a boom (10) and a bucket (11) operated in accordance with the drive of the boom hydraulic actuator (2) and the bucket hydraulic actuator (3) respectively; boom operation means (4) and bucket operation means (5) provided correspondent with the boom hydraulic actuator (2) and the bucket hydraulic actuator (3) respectively; and a boom operation valve (6) and a bucket operation valve (7) which change opening amounts thereof in accordance with operating amounts of the boom operation means (4) and the bucket operation means (5), and which supply pressured oil to the boom hydraulic actuator (2) and the bucket hydraulic actuator (3) respectively, at a flow rate in accordance with the respective opening amounts, wherein
the machine comprises: front-to-rear differential pressure constant means (8, 9) connected between the hydraulic pump and each of the operational valves which equalize a difference in pressure between a pressure of pressured oil on an upstream side and a pressure of pressured oil on a downstream side of the boom operation valve (6) and the bucket operation valve (7) respectively; and, control means (50, 49) which, when the boom operation means (4) is operated, changes an opening amount of the bucket operation valve (7) in response to the operation amount of the boom operation means (4) in such a way that a posture of the bucket (11) is held constant.
A description of the second invention is given below with reference to FIG. 1 and FIG. 3.
According to the second invention, the differential pressure xcex94P between the pressure of the pressured oil on the upstream side and the pressure of the pressured oil on the downstream side of the operation valves 6, 7 is made identical by the front-to-rear differential pressure constant means 8, 9. As a result, from the above-noted formula (1)(Q=cxc2x7Axc2x7{square root over ( )}(xcex94P)), the flow rates Q1, Q2 of the operation valves 6, 7 are determined univocally, irrespective of load fluctuations, that is to say, fluctuations in xcex94P, in accordance with the opening surface areas (opening amounts) A1, A2 of the operation valves 6, 7.
When the boom operation means 4 is operated, the opening amount A2 of the bucket operation valve 7 alters in response to the operation amount S1 of the boom operation means 4 in such a way that the posture of the bucket 11 is held constant.
That is to say, the ratio of the opening amount A1 of the operation valve 6 and the opening amount A2 of the operation valve 7 with respect to the operation amount S1 of the boom operation means 4 is, as shown in FIG. 3(b), set to a fixed relationship (b:a). By virtue of this, the ratio of the flow rate Q1 supplied to the boom hydraulic cylinder 2 correspondent with the boom operation valve 6 and the flow rate Q2 supplied to the bucket hydraulic cylinder 3 correspondent with the bucket operation valve 7 is the above-noted constant relationship (b:a). As a result, the posture of the bucket 11 is held constant.
According to the second invention, as described above, the bucket hydraulic cylinder 3 and the boom hydraulic cylinder 2 can be simultaneously driven at a constant flow rate ratio by only the operation of the boom operation means 4, and the posture of the bucket 11 can be set constant.
In this case, since the ratio of the opening amount A1 of the boom operation valve 6 and the opening amount A2 of the bucket operation valve 7 with respect to the operation amount S1 of the boom operation means 4 only needs to be set to a constant relationship, the device configuration such as the laying of the pressured oil conduits is simple. That is to say, for example, a shuttle valve 50 and a pilot conduit 18b only should be newly provided such that the pilot pressure P can be supplied to the operation valves 6, 7 in accordance with the operation amount S1. In addition, the operation valves 6, 7 (the spool thereof) should be configured in such a way that the ratio of the opening amounts A1, A2 of the operation valves 6, 7 form a constant relationship.
In addition, according to the second invention, the shuttle valve 50 and the pilot conduit 18b only should be newly provided, and the operation valves 6, 7 (the spool thereof) need only to be configured in such a way that the ratio of the A2 of the operation valve 7 and the opening amount A1 of the operation valve 6 with respect to the operation amount S1 of the boom operation means 4 is set to a constant relationship. For this reason, it can be installed easily in existing hydraulic circuits.
In addition, according to the second invention, since the pilot pressured oil, of low pressure and small flow rate, is used, the hydraulic apparatus can be compacted.
As a result, according to the second invention, a high versatility can be obtained, the pipe laying can be configured easily and, by the management of the pilot pressured oil, the hydraulic apparatus can be compacted.
In addition, a third invention is characterized in that, in the second invention the control means (50, 49), when a boom operation signal is output from the boom operation means (4) to afford a lift operation of the boom (10), generates a bucket operation signal which affords the actuation of the bucket (11) in a dumping direction in response to the boom operation signal, and changes the opening amount of the bucket operation valve (7) in response to the bucket operation signal.
A description of the third invention is given below with reference to FIG. 1.
According to the third invention, when a boom operation signal is emitted from the abovementioned boom operation means 4 to afford the lift operation of the abovementioned boom 10, a bucket operation signal is generated which affords the actuation of the abovementioned bucket 11 in the dumping direction in response to said boom operation signal, and the opening amount A2 of the abovementioned bucket operation valve 7 is altered in accordance with said bucket operation signal.
According to the third invention, automatic actuation in the dumping direction to the bucket 11 is performed by the operation of the boom operation means 4 in such a way that the boom 10 is lift-actuated, whereby the posture of the bucket 11 can be held constant.
In addition, the fourth invention is characterized in that, in the second invention, stroke stoppage detection means (35) which is connected to the boom operation valve and detects the stroke stoppage of the boom hydraulic actuator (2) is further provided, and wherein, when the stroke stoppage of the hydraulic actuator (2) has been detected by the stroke stoppage detection means (35), the control by the control means (50, 49) is turned off.
A description is given below of the fourth invention with reference to FIG. 2.
According to the fourth invention, when the stroke stoppage of the boom hydraulic cylinder 2 has been detected by the stroke stoppage detection means 35, and when control is performed by the control means 50, 49, in other words, the boom operation means 4 has been operated, the control which alters the opening amount A2 of the bucket operation valve 7 in response to the operation amount S1 of the boom operation means 4 is switched OFF in such a way that the posture of the bucket 11 is held constant.
According to the fourth invention, the same effects as the second invention are obtained.
Further according to the fourth invention, it can be prevented that the posture of the bucket 11 is not held constant by the continued supply of the pressured oil to the bucket hydraulic cylinder 3 following the stroke stoppage of the boom hydraulic cylinder 2.
That is to say, the control by the control means 50, 49 constitutes a control whereby a flow rate of pressured oil, in accordance with the operation amount S1, is supplied to the boom hydraulic cylinder 2 and bucket hydraulic cylinder 3 in response to the operation of the boom operation means 4. For this reason, even following the stroke stoppage of the boom hydraulic cylinder 2 and the stoppage of the operation of the boom 10, as long as the boom operation means 4 is operated, the supply of the flow rate of pressured oil to the bucket hydraulic cylinder 3 in accordance with the operation amount S1 thereof will be continued and the bucket 11 will continue to be actuated. For this reason, the posture of the bucket 11 will not remain constant.
Thereupon, in the fourth invention, when the stroke stoppage of the boom hydraulic cylinder 2 is detected by the stroke stoppage detection means 35, the supply to the bucket hydraulic cylinder 3 of the pressured oil at a flow rate in accordance with the operation amount S1 of the boom operation means 4, is stopped. More specifically, a flow rate of pressured oil, in accordance with the operation amount S2 of the bucket operation means 5, is supplied to the bucket hydraulic cylinder 3. For this reason, as soon as the operation of the boom 10 is stopped, the actuation of the bucket 11 becomes dependent on the operation amount S2 of the bucket operation means 5. By virtue of this, when the operation amount S2 of the bucket operation means 5 is 0, the posture of the bucket 11 is held constant.
In addition, a fifth invention is characterized in that, in the second invention, it further comprises exhaust flow rate control means (39) that is connected to the bucket operation valve for controlling a flow rate of pressured oil exhausted from the bucket hydraulic actuator (3) in response to a pressure of pressured oil supplied to the bucket hydraulic actuator (3), in such a way that a posture of the bucket is held constant.
A description is given below of the fifth invention with reference to FIG. 2.
According to the fifth invention, the same effects as the second invention are obtained.
Further, according to the fifth invention, the actuation of the bucket 11 by its own weight and displacement from the constant posture of the bucket 11 can be prevented.
That is to say, when the bucket 11 is actuated by its own weight and not by the pressured oil supplied from the hydraulic pump 1, displacement of the constant posture of the bucket 11 occurs.
Therefore, according to the fifth invention, if the pressured oil from the hydraulic pump 1 is supplied to the bucket hydraulic cylinder 3 and the pressure of the pressured oil is above a constant value, the flow rate of the pressured oil exhausted from the bucket hydraulic cylinder 3 is, without control, exhausted to a tank 23. In addition, when the pressured oil from the hydraulic pump 1 is not supplied to the bucket hydraulic cylinder 3 and the pressure of the pressured oil exceeds a constant value, the flow rate of the pressured oil exhausted from the bucket hydraulic cylinder 3 is controlled. By virtue of this, the actuation of the bucket 11 by its own weight is prevented. As a result, the actuation by its own weight and displacement from the constant posture of the bucket 11 is prevented.